1. Field of the Invention
The invention concerns novel catalysts for activating hydrogen peroxide bleaching, detergent compositions containing the novel catalysts and a method for bleaching and/or cleaning substrates employing the aforementioned compositions.
2. The Related Art
Peroxide bleaching agents for use in laundering have been known for many years. Such agents are effective in removing stains, such as tea, fruit and wine stains, from clothing at or near boiling temperatures. The efficacy of peroxide bleaching agents diminishes sharply at temperatures below 60.degree. C.
It is known that many transition metal ions catalyze the decomposition of H.sub.2 O.sub.2 and H.sub.2 O.sub.2 -liberating percompounds, such as sodium perborate. It has also been suggested that transition metal salts together with a chelating agent be employed to activate peroxide compounds to render them usable for satisfactory bleaching at lower temperatures. Not all combinations of transition metals with chelating agents are suitable for improving the bleaching performance of peroxide compound bleaches. Many combinations indeed show no effect, or even a worsening effect, on the bleaching performance; no proper rule seems to exist by which the effect of metal ion/chelating agent combinations on the bleaching performance of peroxide compound bleaches can be predicted.
All these prior art suggestions are based on systems in which free metal ion is the catalytically active species and consequently produce results in practice that are often very inconsistent and/or unsatisfactory, especially when used for washing at low temperatures.
For a transition metal to be useful as a bleach catalyst in a detergent bleach composition, the transition metal compound must not unduly promote peroxide decomposition by nonbleaching pathways and must be hydrolytically and oxidatively stable.
Hitherto the most effective peroxide bleach catalysts are based on cobalt as the transition metal.
The addition to detergent formulations of catalysts based on the transition metal cobalt is, however, a less acceptable route as judged from an environmental point of view.
In a number of patents the use of the environmentally acceptable transition metal manganese is described. All these applications are, however, based on the use of the free manganese ion and do not fulfill the requirement of hydrolytic stability. U.S. Pat. No. 4,728,455 discusses the use of Mn(III)-gluconate as peroxide bleach catalyst with high hydrolytic and oxidative stability; relatively high ratios of ligand (gluconate) to Mn are, however, needed to obtain the desired catalytic system. Moreover, the performance of these Mn-based catalysts is inadequate when used for bleaching in the low temperature region of about 20.degree. to 40.degree. C., and they are effective only against certain stains.
We have now discovered a class of well-defined transition metal complexes which fulfill the demands of stability (both during the washing process and in the dispenser of the washing machine), and which are extremely active, even in the low temperature region, for catalyzing the bleaching action of peroxy compounds on a wide variety of stains.
More recently, there has been disclosed in copending U.S. Pat. applications Ser. Nos. 07/703,554 and 07/703,555, both to Favre et al. each filed May 21, 1991, a series of manganese complexes with dinuclear manganese surrounded by coordinating ligands, especially 1,4,7-trimethyl-1,4,7-triazacyclononane (Me-TACN), having oxygen bridges between the metal centers. These complexes are extremely active, even at low temperatures in catalyzing peroxy compounds. A wide variety of laundry stains are removable through these materials.
While the dinuclear manganese complex catalysts are a substantial advance in the art, the cost of these materials is rather high. Additionally, it would be desirable to find alternative catalysts that are effective with lower levels of peroxy compounds (e.g. perborate) and that would improve performance in removing hydrophobic stains such as tomato sauce.
Consequently, it is an object of the present invention to provide an improved transition metal catalyst for the bleach activation of oxidants, especially peroxy compounds, including hydrogen peroxide and hydrogen peroxide liberating or generating compounds, as well as peroxyacid compounds including peroxyacid precursors, over a wide class of stains at lower temperatures.
Another object of the present invention is to provide an improved bleach-containing detergent composition which is effective to clean laundry at relatively low temperatures.
Still another object of the present invention is to provide an aqueous laundry wash media containing new, improved detergent bleach formulations.
A further object of the present invention is to provide an improved bleaching system comprising a peroxy compound bleach and a transition metal catalyst for the effective use in the washing and bleaching of substrates, including laundry, dentures and hard surfaces (such as in machine dishwashing, general cleaning etc.), and in the textile, paper and wood pulp industries and other related industries.
A still further object of the present invention is to provide a method for bleaching substrates such as laundry; hard surfaces, including dishware; dentures; textiles; paper and pulp; and other substances through use of a novel transition metal catalyst and a peroxy compound bleach.
These and other objects of the present invention will become more apparent through the following description of select embodiments, features and advantages which are described below.